This invention relates to an extrusion head for producing synthetic and the like textile yarns.
Currently known are apparata for spinning conventional polypropylene fibers, of either circular or non-circular cross-section, which can produce directly from the granule a polypropylene staple which is crimped and cut and has good technical properties.
Such apparata include in general an extrusion head, internally whereto one or more feeding chambers are arranged which are provided with dies having calibrated holes distributed across them.
Said currently known dies have a substantially rectangular configuration, thereby serious problems are encountered in obtaining a uniform distribution of the plastics material stock, which is introduced at a central position, all over the die surface.
The difficulty of providing an even distribution of the plastics material across the die surfaces leads to several shortcomings, the first of which results from a degree of uneveness in the quality of the extruded material, which is in the form of a yarn and is then subjected to further processing steps, not discussed herein because beyond the scope of this invention.
Several techniques have been utilized thus far in an attempt to achieve a more even distribution of the plastics across the dies during the feeding process, but these have failed to solve the problem in any radical manner, thereby rectangular shape dies unavoidably develop preferential areas for the passage of the plastics, thus resulting in the production of uneven yarns.
Another problem presented by rectangular shaped dies is that the blowers which direct air at a preset temperature onto the yarns as these emerge from the extruder are of complex construction, since they are required to impinge in a substantially even manner on the group of yarns emerging from the extruder.